About endometriosis

Endometriosis is a common long-term (chronic) condition where tissue similar to the lining of the womb is found elsewhere in the body.

Each month, this tissue responds to the monthly menstrual cycle in the same way as the lining of the womb. The lining builds up, then breaks down followed by bleeding.

But unlike the lining of the womb, which leaves the body as a period, the tissue has no way of leaving the body.

It can be found in many different areas of the body, including:

  • the lining of the inside of the pelvis
  • the ovaries (endometrioma cysts)
  • the bowel or bladder
  • the diaphragm
  • in caesarean section scars

While endometriosis is generally found within the pelvic cavity, it's sometimes found in other parts of the body, such as the lungs.

The condition is estimated to affect around 1.5 million women in the UK.

Symptoms of endometriosis

Symptoms can vary significantly from person to person. Some people have no symptoms at all.

The most common symptoms include:

  • painful periods
  • pain in the lower abdomen (tummy), pelvis or lower back
  • pain during and after sex
  • difficulty getting pregnant
  • discomfort when going to the toilet

Symptoms may be associated with your period or a certain point in the menstrual cycle, rather than being continual.

Other symptoms may include:

  • persistent exhaustion and tiredness (fatigue)
  • bleeding from your back passage (rectum) or blood in your poo (usually at the same time as your period)
  • coughing blood - in less common cases, when the endometriosis tissue is in the lung

The symptoms don't necessarily reflect how much endometriosis tissue a person has. A small amount could be more painful than a large amount.

Diagnosing endometriosis

It can be difficult to diagnose because symptoms can vary considerably and many other conditions can cause similar symptoms.

See your GP if you have symptoms so they can try to help you. Keeping a pain and symptoms diary can help you describe to your GP what you are experiencing.

If your GP suspects endometriosis, you may be prescribed pain relief and hormonal contraceptives, such as the contraceptive pill, injection or hormonal coil (IUD) to try and control the symptoms.

Referral to a specialist

If symptoms continue, you have side effects that negatively affect you or you don't want to use hormonal treatment, your GP may refer you to a gynaecologist. This is a doctor specialising in problems affecting the female reproductive system.

Your gynaecologist will ask about your symptoms, your periods and possibly if you experience pain or discomfort during sex.

They may also carry out an internal pelvic exam or recommend an ultrasound scan to look for endometriosis-related cysts in your ovaries (endometrioma).

Causes of endometriosis

The cause of endometriosis is unknown, but there are several theories.

Retrograde menstruation

Retrograde menstruation is when the womb lining (endometrium) flows backward through the fallopian tubes and into the abdomen (tummy) instead of leaving the body as a period.

In endometriosis, it's thought this tissue can then embed itself on the organs of the pelvis and grow.

Retrograde menstruation happens in most women, but why it may attach and grow in some women and lead to endometriosis isn't known.


Endometriosis is sometimes believed to be hereditary, being passed down through the genes of family members.

If someone in your family has the condition, it's more likely you'll have it too. This suggests genes may play a part.

Spread through the bloodstream or lymphatic system

Although it's unexplained, endometriosis cells are believed to get into the bloodstream or lymphatic system (the immune system network of vessels and glands).

This could explain how, occasionally, the cells are found in places such as the lungs.


Metaplasia is the process of one type of cell changing into another to adapt to its environment. It's this development that allows the human body to grow in the womb before birth.

It's been suggested some adult cells may retain this ability to change. When menstrual blood enters the pelvis during a period, it may stimulate them to transform into endometriosis cells.

Environmental causes

It's thought the condition may be caused by certain toxins in the environment, such as dioxins, that affect the immune system and reproductive system.

Research studies have shown that when animals were exposed to levels of dioxin, they developed endometriosis.

This theory has not yet been proven for humans.

Treating endometriosis

There is no cure for endometriosis and it can be difficult to treat. Treatment aims to ease symptoms so the condition doesn't interfere with your daily life.

Treatment will be given to control or improve symptoms and improve fertility.

Deciding which treatment

Your gynaecologist will discuss the treatment options with you and outline the risks and benefits of each.

When deciding which treatment is right for you, you should consider:

  • whether your main symptom is pain or difficulty getting pregnant
  • whether you want to become pregnant, as some treatments may stop you from getting pregnant
  • how you feel about surgery
  • whether you've tried any of the treatments before

You may choose not to have treatment if your symptoms are mild, you have no fertility problems or if you're nearing menopause, when symptoms may get better without treatment.

One course of action is to keep an eye on symptoms and decide to have treatment if they get worse.

Support from Endometriosis UK can be very useful if you're learning how to manage the condition.

Pain medication

Paracetamol and Non-steroidal anti-inflammatories (NSAIDs), such as ibuprofen and naproxen, can be used to treat the pain associated with endometriosis.

NSAIDs can cause side effects, such as nausea, vomiting and diarrhoea.

Codeine is a stronger painkiller that's sometimes combined with paracetamol or used alone if other painkillers aren't suitable. However, constipation is a common side effect, which may aggravate the symptoms of endometriosis.

For more information, read the Endometriosis UK factsheet on pain relief for endometriosis

Hormone treatment

The aim of hormone treatment is to manage the oestrogen in your body.

This is because the hormone oestrogen controls the menstrual cycle and also encourages endometriosis tissue to grow and shed. Without exposure to oestrogen, symptoms can be reduced.

Hormone treatment has no effect on adhesions – scar tissue that can cause organs to fuse together – that have already formed, and it can't improve fertility.

Some of the main hormone-based treatments include:

Evidence suggests these hormone treatments are equally effective at treating endometriosis, but they have different side effects.

Although most hormone treatments reduce your chance of pregnancy while using them, only the contraceptive pill or patch and LNG-IUS are licensed to be used as contraceptives.

Progestogens and antiprogestogens are used less commonly, for people who can't take oestrogen.

The combined oral contraceptive pill or patch

The combined contraceptive pill and contraceptive patch contain the hormones oestrogen and progestogen.

They can be used long-term and stop eggs from being released (ovulation) to make periods lighter and less painful.

These contraceptives can have side effects, but there are several different types available.

Learn more about the combined contraceptive pill or patch

Levonorgestrel-releasing intrauterine system (LNG-IUS) – hormonal coil

The Mirena levonorgestrel-releasing intrauterine system (LNG-IUS) is a T-shaped contraceptive device that fits into the womb, often referred to as a coil.

It releases a type of progestogen hormone called levonorgestrel and greatly reduces or even stops periods.

The device is put into the womb by a doctor or nurse. Once in place, it can remain effective for up to 5 years.

Possible side effects of using LNG-IUS include irregular bleeding that may last more than 6 months, breast tenderness and acne.

Learn more about the IUS

Gonadotrophin-releasing hormone (GnRH) analogues

GnRH analogues are synthetic hormones that bring on temporary menopause by reducing the production of oestrogen. They're usually taken as a nasal spray or injection.

Menopause-like side effects of GnRH analogues include hot flushes, vaginal dryness and low libido (sex drive).

Sometimes low doses of hormone replacement therapy (HRT) is recommended in addition to GnRH analogues to prevent these side effects.

They're only usually prescribed on a short-term basis (normally 6 months at a time) and your symptoms may return after treatment is stopped.

GnRH analogues aren't licensed as a form of contraception, so you should still use contraception while taking them.


Progestogens, such as norethisterone, are synthetic hormones that behave like the natural hormone progesterone.

However, they have side effects such as:

  • bloating
  • mood changes
  • irregular bleeding
  • weight gain

Progestogens are usually taken daily in tablet form from days 5 to 26 of your menstrual cycle, counting the first day of your period as day one.

Most progestogen tablets aren't an effective form of contraception, so you'll still need to use contraception while taking them if you don't want to get pregnant.


Also known as testosterone derivatives, antiprogestogens are synthetic hormones. They bring on a temporary artificial menopause by decreasing the production of oestrogen.

Side effects of antiprogestogens can include:

  • weight gain
  • acne
  • mood changes
  • the development of masculine features, such as hair growth and a deepening voice

These side effects are often severe, and alternative medications are more effective. This means antiprogestogens are usually only prescribed as a last resort if other medications haven't worked.


Surgery can be used to remove or destroy areas of endometriosis tissue, which can help improve symptoms and fertility. The kind of surgery you have will depend on where the tissue is.

The types of surgery are:

  • laparoscopy – the most commonly used and least invasive technique
  • laparotomy

Any surgical procedure carries risks. It's important to discuss these with your surgeon before undergoing treatment.


Laparoscopy, also known as keyhole surgery, is a common procedure used to remove endometriosis. Small cuts (incisions) are made in your tummy to insert instruments to see and remove the tissue.

During a laparoscopy, fine instruments are used to apply heat, a laser, an electric current (diathermy) or a beam of special helium gas to the patches of tissue to destroy or remove them.

The procedure is carried out under general anaesthetic, so you'll be asleep and won't feel any pain as it's carried out.

Ovarian cysts, or endometriomas, which are formed as a result of endometriosis, can also be removed using this technique.


While the majority of surgeries for endometriosis are done by laparoscopy, sometimes this is not possible and a laparotomy is undertaken.

During the procedure, the surgeon makes a wide cut along the bikini line and opens up the area to access the affected organs and remove the endometriosis tissue.

Recovery time for this type of surgery is longer than for keyhole surgery.

Complications of endometriosis

Symptoms of endometriosis include pain and infertility. In some cases, endometriosis may result in adhesions or ovarian cysts.

Fertility problems

While many with endometriosis will be able to get pregnant naturally, endometriosis can sometimes damage the fallopian tubes or ovaries, causing fertility problems.

Hormonal medication won't improve fertility.

Surgery to remove patches of endometriosis tissue can help, but there's no guarantee this will allow you to get pregnant.

If you're having difficulty getting pregnant, in vitro fertilisation (IVF) offers a good chance of conception. However, people with endometriosis can have a lower chance of getting pregnant with IVF than those with other conditions.

Adhesions and ovarian cysts

Other complications include the formation of:

  • adhesions – scar tissue that can fuse organs together
  • ovarian cysts – fluid-filled cysts in the ovaries that can sometimes become very large and painful

Both of these complications can be treated with surgery but may come back if the endometriosis returns.

Read information about treating ovarian cysts